Full definition
The irreversible chemical process of creating cross-links between polymer chains in raw rubber, transforming it from a soft, thermoplastic-like material into a strong, elastic, thermoset material with defined mechanical properties (hardness, tensile strength, elongation, compression set). Discovered by Charles Goodyear in 1839 using sulfur and heat. Modern vulcanization systems: (1) Sulfur + accelerators + ZnO/stearic acid — for diene rubbers (NR, SBR, NBR, CR); forms polysulfidic, disulfidic, and monosulfidic cross-links; cure at 140-180°C. (2) Organic peroxides (DCP, DBPH) — for saturated rubbers (EPDM, silicone, HNBR) and non-staining applications; forms C-C cross-links; better heat and compression set resistance. (3) Metal oxides (ZnO for CR, MgO for CSM) — for halogenated rubbers. (4) Platinum catalyst — addition cure for liquid silicone (LSR). Cross-link density determines physical properties: too few = soft, poor recovery; too many = hard, brittle. Cure parameters (temperature, time, pressure) are optimized using MDR rheometer cure curves (t90 = time to 90% cure). Equipment: compression press, injection mold, transfer mold, autoclave, hot-air tunnel, LCM, and rotocure (continuous). Per ISO 3417 and ASTM D5289 for cure characterization.